Re: [PATCH v2] io_uring/rsrc: fix RLIMIT_MEMLOCK bypass by removing cross-buffer accounting

Pavel Begunkov
2026-01-24T16:30:28Z

On 1/24/26 15:55, Jens Axboe wrote:
> On 1/24/26 8:14 AM, Jens Axboe wrote:
>>>> ________________________________________________________
>>>> Executed in 2.81 secs fish external
>>>> usr time 0.71 secs 497.00 micros 0.71 secs
>>>> sys time 19.57 secs 183.00 micros 19.57 secs
>>>>
>>>> which isn't insane. Obviously also needs conditional rescheduling in the
>>>> page loops, as those can take a loooong time for large amounts of
>>>> memory.
>>>
>>> 2.8 sec sounds like a lot as well, makes me wonder which part of
>>> that is mm, but it mm should scale fine-ish. Surely there will be
>>> contention on page refcounts but at least the table walk is
>>> lockless in the best case scenario and otherwise seems to be read
>>> protected by an rw lock.
>>
>> Well a lot of that is also just faulting in the memory on clear, test
>> case should probably be modified to do its own timing. And iterating
>> page arrays is a huge part of it too. There's no real contention in that
>> 2.8 seconds.
>
> I checked and the faulting part is 2.0s of that runtime. On a re-run:

Makes sense, I was forgetting it's full time.

--
Pavel Begunkov